This invention relates generally to knife blades, and more particularly, is directed to the formation of surgical knife blades.
In order to produce surgical blades, for example, for microsurgery and special surgery such as eye, ENT (ear, nose and throat), neurological, vascular, OB/GYN and the like, blanks having the desired shape of the blade are first cut from a section of soft flat stock of stainless steel or the like in a variety of thicknesses on the order of 0.0015 inch to 0.095 inch. This has conventionally been performed by forging dies, or use of male and female cutting dies, or alternatively, by a wire EDM method which uses an electrical discharge to burn through the material. This, of course, in the case of the cutting dies, requires specially designed and expensive tooling, such as perforating dies, stamping dies or forging dies, in addition to other equipment. In practice, a single or a plurality of blanks are cut simultaneously from the same section of flat stock. Then, the blanks are sequentially straightened, hardened, tempered and tumbled to remove burrs and discoloration, sharpened by grinding and then buffed to smooth the ground edge. As to the grinding step, a variety of grinding wheels are used, such as a 38A grade A10 wheel sold by Norton.
This process, however, has various disadvantages. First, because the blanks are either die cut or electrically cut from the flat stock, the shapes of the blanks may not be as precise as desired. Related thereto, the blanks that are produced by the aforementioned dies are inherently not flat. This is because the dies push through the metal with a force. Thus, as a result, mechanical stresses are also introduced into the blank material. Further, the blanks are formed with burrs which must be removed. Accordingly, the aforementioned additional step of tumbling is required. However, since the blanks must have certain critical tolerances of for example .+-.0.003 inch, this blanking step is not very precise.
In addition, when cutting the blanks in accordance with the aforementioned known processes, soft or semihard stainless steels are commonly used, since the dies or electrical discharge will not satisfactorily and efficiently cut through a hard stainless steel. As a result, it may be necessary to straighten the blanks after they are cut. Further, the blanks must be tempered to achieve alignment of the metal grain structure, which is necessary to achieve proper hardness for the later sharpening operation. This is performed by the rolling and heat treating steps discussed above, prior to the tumbling step.
Because the heat-treated and tempered blanks have a discoloration due to oxidation, they must be treated in specially designed ovens and furnaces with individually suited atmospheric or vacuum conditions. As such, the blanks are chemically treated to minimize such oxidation and discoloration. The blanks are then chemically or mechanically cleaned.
Further, because the dies occupy space, sufficient room must be provided between blanks to be cut to accommodate the dies. This, of course, results in a waste of material in the flat stock.
It may also be desirable to place markings on the knife blades, such as a logo or the like. With the aforementioned methods of forming knife blades, an additional die is necessary to mechanically insert the logo in the knife blades. In addition to adding to the costs, this additional step may also slightly distort the knife blades and add additional stresses therein, which may result in breaking of the blades. Further, the markings are sometimes distorted to some extent due to mechanical warping.
It will be appreciated that the above known methods require expensive capital equipment, and each of the steps must be carefully monitored for hardness, finish, and the like.
Of interest to the present invention are U.S. Pat. Nos. 3,916,749 and 3,696,013.